Free-bubble gas sound source



April 12, 1966 D. T. BARRY FREEFBUBBLE GAS SOUND SOURCE INVENTOR David 7.' Barry M M y iTTORNEYS Filed Oct. 16, 1962 April 12, 1966 D. 'r. BARRY FREE-BUBBLE GAS SOUND SOURCE 2 Sheets-Sheet 2 Filed Oct. 16, 1962 F &'

INVENTOR Danni 75a?? [III JZWIQJ M m M ATTORNEYS United States Patent 3,246,286 FREE-BUBBLE GAS SOUND SUURCE David T. Barry, Dalias, Tern, assignor to Texas Instruments Incorporated, Dallas, Tex, a corporation of Delaware Filed Get. 16, 1962, Ser. No. 230,954 10 Claims. (Cl. 340-7) This invention relates to a sound source and more specifically to a. free bubble gas sound source for generating high energy acoustic pulses in water.

- Many attempts have been made in the past to generate high energy acoustic pulses in water. For example, one of the prior art attempts to solve this problem employs a partly submerged vertical tube wherein a mixture of gas is exploded in the top portion thereof to produce a sound Wave which travels down the tube and then into the surrounding aqueous medium. This system requires a bulky, high hydrodynamic drag tube. Furthermore, the. fact that the gas mixture is exploded in the top portion of the tube, requiring that the sound travel down the tube, causes a loss in the sound energy developed and tends to heat up the tube. The explosion approximates an air burst rather than an underwater burst since the explosion takes place Within the tube with consequent energy losses at the interface. Furthermore, the acoustic spectrum of the pulse is modified by the tube so that the approximation to a true impulse is less with the above-mentioned system than with a free bubble gas sound source. Finally, the tube of the above prior art system must be able to withstand explosions without rupturing since the explosions take place therein.

In accordance with this invention, unmixed fuel and oxygen lines are attached to a submerged towed vessel which contains an impeller for driving a mixing wheel, an intermittently opened exhaust port, a firing switch responsive to the speed of the impeller and a firing line upon which bubbles exhausted from the exhaust port can be exploded.

The gases are mixed within a mixing chamber in the towed vessel to form an explosion mixture. When the exhaust port is opened, the explosion mixture is released since the pressure in the mixing chamber is in excess of hydrostatic pressure. The mixture forms a bubble which is set free when the exhaust port is closed. Thebubble then moves along the insulated portion of the firing line due to drag, buoyancy and surface tension until it is positioned adjacent a bare portion on the firing line, at which time the firing switch is closed. A firing pulse is produced which explodes the bubble thereby producing an underwater acoustic pulse.

It is an object of this invention to provide a simple, economic method of generating a high energy acoustic puise in water.

It is another object of this invention to provide a free bubble gas sound source which eliminates the need for a longtu'oe to contain the explosive mixture.

It is a further object of this invention to provide a system having increased efiiciency of energy transfer by creating the explosion in the water.

It is a still further object of this invention to provide a system to eliminate any hazard in the use of an explosive mixture by mixing of the gases at a point remote from the towing vessel.

It is yet a further object of this invention to eliminate the need for gas transfer or mixing pumps and for separate timing circuits.

It is yet another object of this invention to provide a system for reducing the amount of firing pulse energy 7 required by having a relatively short firing pulse transmission path.

Patented Apr. 12, 1966 Other advantages and objects of this. invention will be readily apparent to those skilled in the art by refer ence to the following detailed description when considered in connection with the accompanying drawings in which like reference numerals designate like parts throughout the figures thereof and wherein:

FIGURE 1 is a diagram of the sound source of this invention in combination with its towing ship and a surface buoy;

FIGURE 2 is a cross-sectional view of the free bubble gas sound source of this invention; and

FIGURE 3' is a schema-tic diagram of the electric circuit employed in the present invention.

Referring to the drawings, and in particular FIGURE 1, the general organization of the invention is shown as comprising a submerged towed body 1, a surface buoy 2 and a towing vessel 3. A towing line 4. interconnects the vessel 3 with buoy 2' and a' towing line 5 intercomnects buoy 2 with the submerged body 1.

The body 1 is shown insection in FIGURE 2 and consists of a housing divided internally by a wall 11 into two compartments. A shaft 12 projects through the forward end of housing 10 and an impeller 13 is fixed to the projecting end of shaft 12. A suitable bearing 14 is positioned between shaft 12 and housing 10 to enable shaft 12 to be freely rotatable. Shaft 12 projects through wall 11 and is journalled in a bearing box 15. A box 16 containing suitable seals and bearings is mounted on the shaft 12 adjacent wall 11. A propeller or mixing wheel 17 is fixed to shaft 12 between wall 11 and box or in the after compartment. As evident from the foregoing explanation, forward movement of body 1 through water will drive the impeller 13' and, in turn, drive shaft 12 and propeller 17.

In the forward compartment, a spur gear 20 is fixed to shaft 12. and meshes with a spur gear 21 fixed on one end of shaft 22. A conventional cam-operated micro switch is contained in a box 23 and the cam is driven by shaft 22.

In the after compartment, a spur gear 3t) is fixed to shaft 12 and meshes with a spur gear 31 fixed on one end of shaft 32. A box 33 containing a suitable cam is mounted in the after compartment and shaft 32 is connected to drive the cam. Housing 16) is provided with a well the bottom of which defines a port. A closure element 41 is seated in the well 49 normally closing the port and is connected by a rod 42 to the follower for the cam in box 33. Hence, the cam in box 33, acting through its follower and rod 42, periodically unsea-ts the closure element 41 and allows gas in the after compartment to escape via the port.

A curved tube 50 is attached to housing 10 about an opening therein and projects upwardly above well 40 and terminates aft of well 40. Gases released through the port in well 4% will form a bubble that will adhere to tube 50 and travel along its length. A spark gap 51 is fixed to the free end of tube 5% and connected by electrical wires 52 to the microswitch in box 23. Wires 52 are sealed in the wall of housing 10 to prevent gas escape through tube 50.

The upper forward end of housing 10 is formed as a projection and the towline 5 is connected to the end of this projection. Towline 5 is composed of a towing cable 60 attached to the projection of housing 10 by a fitting 61, an oxygen hose 62, a fuel hose 63, and an electrical cable 64. A helical wrap serves to hold the component parts of towline 5 together. The two hoses 62 and 63 are coupled through openings in the housing It with tubes 0 66 and 67, respectively, which are fitted into openings in wall 11 and discharge into the after compartment. The

electrical cable 64 passes along the upper surface of housw m i W ing and through housing 10 by means of a suitable fitting and connects with box 23.

The buoy 2 contains separate supplies of oxygen under pressure, fuel under pressure, and electric power (battery) each of which is connected to the appropriate component part of towline 5.

The electrical circuit for the apparatus is shown in FIGURE 3 and comprises a battery 70 located in buoy 2, a microswitch 71 located in box 23, and a spark gap 51 located on the end of tube 50. Switch 71 is operated by 10 a cam 72 also contained in box 23. The electrical cable 64 and electrical wires 52 electrically interconnect switch 71, battery 70, and spark gap 51 in the manner shown in FIGURE 3.

The free bubble gas sound source is operated in the following manner. Fuel and oxygen are continually transferred from the oxygen tank and the fuel tank in buoy 2, both maintained at a pressure above hydrostatic pressure, through the fuel lines 63 and 67 and the oxygen lines 62 and 66, and enter the after compartment or mixing chamber in body 1. Since the submerged body 1 and the surface buoy 2 are towed by a surface craft '3, the shaft 12 is rotated by the force exerted on the impeller 13 due to the movement of the submerged body through the water. The rotation of the shaft 12 causes the mixing wheel 17 to be rotated within the mixing chamber and mix the incoming gases from the fuel line 67 and the oxygen line 66 to produce mixture uniformity. The shaft 12 also drives the gears 30 and 31 positioned thereon. Rotation of the gear 31 causes rotational movement of the cam in box 33 through the shaft 32 to open and closeintermittently the exhaust port in well 44) due to the movement imparted to the closure member 41 by the cam in box 33. The shaft 12 also drives the cam 72 in box 23 through the gears 20 and 21 and the shaft 22 to open and close intermittently the microswitch 71 in box 23. The rate of the opening and closing of'the port in Well 40 and the microswitch 71 is dependent upon the gear ratios, the amount of eccentricity in the cams and the speed of the towing vessel.

Closure of the microswitch 71 causes a firing potential to be applied from battery 70 to spark gap 51 at the end of tube 50, the closure being delayed until the shaft 12 has made a predetermined additional number of revolutions after the closure of the exhaust port in well 40.

When the exhaust port in well 40 is opened by the action of the cam in box 33 in unseating closure element 41, the exposive fuel and oxygen mixture is exhausted from the mixing chamber, since the pressure in the mixing chamber is in excess of hydrostatic pressure, and forms a bubble which is freed from the exhaust port when the port is closed by the closure element 41 seating responsive to a further revolving of the cam in box 33. The bubble is pulled along the tube 50 due to drag, buoyancy and surface tension until it reaches the spark gap 51 at the end of tube 50. The spark gap 51 has a firing potential 55 applied thereto at this time due to the delay built into the gear system, and a spark is generated in gap 51 to fire the bubble and thereby cause an explosion.

It should be noted that a semicircular shielding device may be employed to guide the bubble in contact with the tube 5t). If a stationary source is desired, an almost vertical firing line would be employed since buoyancy alone would move the bubble upwardly of the firing line. Since only relatively small bubbles can be generated in the free state, an additional section can be added to the subsurface body to store and mechanically attach a balloon or other expansible device to the exhaust port. The balloon would then be inflated by the gaseous mixture forming a large contained bubble and the mixture detonated in the same fashion as the free bubble.

The gears 20, 21, 30 and 31 are designed so that the cams in boxes 23 and 33 will close the microswitch 71 at that point in time when the bubble is positioned adjacent the spark gap 51, thereby connecting the voltage source 70 positioned in the surface buoy 2 across the spark gap 51 to produce a firing pulse for exploding the gas mix- I tended duration determined by the shape of the cam 72 in order to insure the application of the potential to the gap 51 when the bubble is positioned thereon.

In accordance with this invention, explosions can be produced at equally spaced points in the fluid medium. This is true irrespective of any change or variation in speed of the towed body 1.

The fuel fed to the mixing chamber by the fuel lines 63 and 67 includes gaseous hydrocarbons such as propane, acetylene and methane.

It should also be noted that a group of devices as described supra with exhaust ports pointing in different directions or a unitary device as set forth supra with a plurality of exhaust ports pointing in different directions may be employed in the nature of a seismic array so that direc- 20 tional characteristics maybe utilized.

Although the invention has been described with respect to a specific embodiment, many variations will be obvious to those skilled in the art. Accordingly, it is the intention to be limited only as indicated by the scope of the following claims which are to be interpreted as broadly as possible in view of the prior art.

What is claimed is:

1. A repetitive underwater sound source towed through a liquid medium at a certain speed which includes an em closed chamber a portion of which is submerged in said liquid medium, means to feed fluids into said chamber, means to mix said fluids to produce an explosive mixture in said chamber, means responsive to a predetermined condition for exhausting a bubble of said fluid mixture 35 from the submerged portion of said chamber into said liquid medium, and means responsive to a second prede termined condition for exploding said gaseous mixture in said bubble externally of said chamber at substantially equal distances in said fluid medium irrespective of changes in the speed of said submerged portion.

2. A repetitive underwater sound source towed through a liquid medium at certain speed which includes an enclosed chamber a portion of which is submerged in said liquid medium, means for feeding gases into said chamber and maintaining a gaseous pressure within said chamher higher than the hydrostatic pressure on the submerged portion of said chamber, means for mixing said gases to produce an explosive mixture, means responsive to a predetermined condition for exhausting a bubble of said gaseous mixture from the submerged portion of said cham her into said liquid medium, and means responsive to a second predetermined condition for exploding said gaseous mixture bubble externally of said chamber at substantially equal distances in said fluid medium irrespective of changes in speed of said submerged portion.

3. A repetitive underwater sound source towed through a liquid medium at a certain speed which includes an enclosed chamber a portion of which is submerged in said liquid medium, means for feeding gases into said chamber and maintaining a gaseous pressure within said chamber higher than the hydrostatic pressure on the submerged portion of said chamber, means for mixing said gases to produce an explosive mixture, means responsive to a predetermined condition for exhausting a bubble of said gaseous mixture from the submerged portion of said chamber into said liquid medium, and means responsive to the speed of travel of said chamber in said liquid medium for exploding said gaseous mixture bubble externally of said chamber at substantially equal distances in said fluid medium irrespective of changes in speed of said submerged portion.

4. An underwater sound source as set forth in claim 3 wherein said means for exploding includes a source of electrical potential,

5. A repetitive underwater sound source towed through a liquid medium at a certain speed which includes an enclosed chamber adapted to be submerged in said liquid medium, means for feeding gases into said chamber and maintaining a gaseous pressure which is higher than the hydrostatic pressure on said submerged chamber, means for mixing said gases to produce an explosive mixture, first means responsive to the speed of travel of said chamber through said liquid medium for exhausting a bubble of said gaseous mixture from said chamber into said liquid medium, and second means responsive to the speed of travel of said chamber through said liquid medium for exploding said gaseous mixture bubble externally of said chamber at substantially equal distances in said fluid medium irrespective of changes in speed of said submerged portions.

6. An underwater sound source which includes a housing defining an enclosed chamber and an aperture therein, a closure element for said aperture, said housing adapted to be submerged in a liquid medium, means for feeding gases into said chamber and maintaining a pressure within said chamber which is higher than the hydrostatic pressure on said chamber when submerged, means for mixing said gases to produce an explosive mixture, rotatable means mounted in said chamber for rotating at a speed proportional to the speed of travel of said chamber in said liquid medium, first means responsive to a predetermined rotation of said rotatable means for actuating said closure element to exhaust a bubble of said gaseous mixture from said chamber into said liquid medium, a firing line positioned externally of said chamber adjacent said aperture and having electrodes thereon, a source of potential, a switch serially connected between said source of potential and said electrodes, and second means responsive to a predetermined rotation of said rotatable means for operating said switch to place a potential on said electrodes for exploding said gaseous mixture bubble externally of said chamber.

7. An underwater sound source as set forth in claim 6 wherein said first means for actuating said closure element includes a cam.

8. An underwater sound source as set forth in claim 6 wherein said second means for operating said switch includes a cam.

9. An underwater sound source comprising a housing defining an enclosed chamber and an aperture, said housing adapted to be submerged in a liquid medium, means for feeding gases into said chamber and maintaining a pressure in said chamber which is higher than the hydrostatic pressure on said housing when submerged, means for mixing said gases to produce an explosive mixture, rotatable means positioned in said chamber adapted to rotate proportional to the speed of travel of said housing through said liquid medium, a first cam, a first gear train connected to drive said cam and operatively driven by said rotatable means, a closure element for said aperture engaged to be moved by said cam so that said cam when rotated moves said closure element to open and close said aperture for exhausting a bubble of said gaseous mixture from said chamber into said liquid medium, a firing line attached to said housing adjacent said aperture and projecting away from said housing, said firing line having at least one contact member thereon, a source of potential, a switch serially connected between said contact and said source of potential, a second cam mounted to actuate said switch, and a second gear train connected to said second cam and operatively driven by said rotatable means for causing said second cam to close said switch and place an electrical potential on said contact when said bubble is positioned substantially adjacent said contact for exploding said gaseous mixture bubble externally of said chamber.

10. An underwater sound source which comprises an enclosed chamber adapted to be submerged in a liquid medium, means for feeding gases into said chamber and maintaining a gaseous pressure which is higher than the hydrostatic pressure on said submerged chamber, means for mixing said gases to produce an explosive mixture, first means responsive to the speed of travel of said chamber through said liquid medium for exhausting a bubble of said gaseous mixture from said chamber into said liquid medium, said first means responsive including a rotatable means responsive to the speed of travel of said chamber I through said liquid medium, a gear train responsive to the speed of rotation of said rotatable means, means responsive to said gear train for opening and closing an aperture defined by said enclosed chamber, and second means responsive to the speed of travel of said chamber through said liquid medium for exploding said gaseous mixture bubble externally of said chamber.

References fired by the Examiner UNITED STATES PATENTS 669,999 3/1901 Mensing 34012 2,353,360 7/1944 Ronning 3404 X 3,039,559 6/1962 Ellsworth 18l0.5 3,093,107 6/1963 Grand et al 11627 3,187,831 6/1965 Smith 340--12 X CHESTER L. JUSTUS, Primary Examiner.

R. A. FARLEY, Assistant Examiner. 

1. A REPETITIVE UNDERWATER SOUND SOURCE TOWED THROUGH A LIQUID MEDIUM AT A CERTAIN SPEED WHICH INCLUDES AN ENCLOSED CHAMBER A PORTION OF WHICH IS SUBMERGED IN SAID LIQUID MEDIUM, MEANS TO FEED FLUIDS INTO SAID CHAMBER, MEANS TO MIX SAID FLUIDS TO PRODUCE AN EXPLOSIVE MIXTURE IN SAID CHAMBER, MEANS RESPONSIVE TO A PREDETERMINED CONDITION FOR EXHAUSTING A BUBBLE OF SAID FLUID MIXTURE FROM THE SUBMERGED PORTION OF SAID CHAMBER INTO SAID LIQUID MEDIUM, AND MEANS RESPONSIVE TO A SECOND PREDETERMINED CONDITION FOR EXPLODING SAID GASEOUS MIXTURE IN SAID BUBBLE EXTERNALLY OF SAID CHAMBER AT SUBSTANTIALLY EQUAL DISTANCES IN SAID FLUID MEDIUM IRRESPECTIVE OF CHANGES IN THE SPEED OF SAID SUBMERGED PORTION. 